This invention relates to a process and apparatus for treating forage material and other agricultural plants by crushing and impact maceration. The treated material exhibits both greater drying rates and digestibility than conventionally treated forage material.
The two most conventional and widely used systems for harvesting forage are: a) mowing and conditioning (drying) followed by baling to produce dry hay, and b) mowing and conditioning followed by chopping to produce silage. However, these two methods typically have losses between the cutting stage and the feeding stage that range from 20 to 30%, which can reduce the quality and profitability of the forage [Savoie et al., Transactions of ASAE, vol. 25, no. 3 (1982), pp. 581-585, 591; Koegel et al., Transactions of ASAE, vol. 28, no. 4 (1985), pp. 1047-1051]. These losses can be classified into: a) losses due to overmaturity, b) losses due to plant respiration during drying, c) mechanical losses including loss of high quality leaves during harvest, d) leaching and other losses due to rain during field curing, e) storage and feeding losses, and f) handling and processing losses.
Processes employing maceration of forage materials of lucerne (alfalfa) have previously been found to increase drying rates and digestibility by ruminants. When macerated, pressed forage material was spread in the sun to dry for hay; it was noted that its drying rate was high relative to that of conventional material. Maceration caused the stems to be split into numerous fibrous pieces while mashing or pureeing the leaves and upper stem segments [Shinners et al., Transactions of ASAE, vol. 30, no. 4 (1987), pp. 909-912]. This resulted in a greatly increased specific surface area, a reduced resistance to moisture removal, and a bruised, darkened material with increased absorption of solar energy [Ajibola et al., Transactions of ASAE, vol. 23, no. 5 (1980), pp. 1197-1300].
Pressed forage fiber of lucerne has also been prepared for feeding trials both in the form of dry hay and as silage to be compared to conventionally prepared hay and silage. When the pressed forage and the control, in the form of silage, were fed to milk cows, contrary to expectation no difference in milk production per unit of dry matter was detectable [Lu et al., J. Dairy Sci., vol. 62 (1979), pp. 1399-1407]. Approximately the same results had been reported by other researchers for hay [Connel and Cramp, Proc. Br. Soc. Anim. Prod., vol. 4 (1975), pp. 112-113]. It has been concluded that the process of maceration allowed the fiber fraction of the forage material, with its high cell wall concentration, to be more extensively digested than the control forage. Later experiments, in which macerated and control lucerne were placed in the rumen of a dairy cow in dacron bags to compare the rate and extent of disappearance, demonstrated that mechanical processing of forage crops could lead to increased digestibility of the fiber fraction. Hong et al. [J. Dairy Sci., vol 71 (1988), pp. 1536-1545, and J. Dairy Sci., vol 71 (1988), pp. 1546-1555] carried out in vitro experiments confirming these results.
Silage as well has been successfully made from macerated lucerne. Shinners et al. [Transactions of ASAE (1988), ibid. ] compared the compaction properties of macerated lucerne with chopped lucerne, and found that macerated lucerne attained higher densities. The higher density of macerated lucerne is considered important in reducing the entrapped oxygen at the time the forage is ensiled, and to prevent the infusion of oxygen and undesirable secondary fermentations when the silo is unloaded. Muck et al. [Proc. 11th C.I.G.R., Dublin, Ireland (1989)] compared the ensiling of mat-harvested lucerne with that of conventionally chopped lucerne. The researchers found that the macerated lucerne fermented more quickly, reaching its final pH in half the time required for the conventionally produced lucerne. Wandel et al. [DLG Mitteilungen, 8 (1990)] found similar high rates of fermentation in macerated grass and in grass-lucerne mixtures.
Machines have been proposed which would: a) mow, b) macerate (severely condition) the forage, c) press the macerated material into thin continuous mats, and d) deposit the intact mats onto the field stubble for drying [Shinners et al., Applied Engineering in Agriculture, vol. 4, no. 1 (1988), pp. 13-18]. The mats of macerated forage could then be harvested by either baling or chopping when the appropriate moisture is reached.
Krutz [U.S. Pat. No. 4,265,076 (1981)] disclosed an apparatus for macerating forage products and pressing the treated forage material into mats for enhanced drying. The apparatus included two cylindrical rollers (17 and 18) rotating in opposite directions at different speeds to macerate the forage material passed therebetween. The macerated products are then conveyed rearwardly between a roller/conveyor (28) and roller (27) for mat formation by pressing. The reference also discloses the use of optional, intermediate fluffer brushes (70 and 71, FIG. 3).
Recently, maceration of crops has been accomplished by passing the forage through a multiplicity of nips between knurled cylindrical surfaces with surface speed ratios of approximately 1.3:1.0 [Shinners et al., Proc. 11th C.I.G.R., Dublin, Ireland (1989), and Koegel et al., Applied Engineering in Agriculture, vol. 4, no. 2 (1988), pp. 126-129]. The number of nips has generally varied between 5 and 7 and the clearances between 0.3 mm and 0.5 mm.
In all of these prior art devices, presses have been provided for forming mats from the macerated material. These presses for forming the mats have generally consisted of either: (1) two belts with the macerated forage between them for running between pressure rolls, or (2) a belt and drum arrangement between which the mat is formed with the aid of pressure rolls forcing the belt toward the drum [Shinners et al. (1989), ibid., and Koegel et al. (1988), ibid.]. As the width of the machines increases to realistic farm sizes, however, belts become more expensive and more difficult to manage.